Composite bow centralizer

ABSTRACT

A centralizer comprises a first collar, a second collar, a plurality of bow springs coupling the first collar to the second collar, and a plurality of particulates disposed on an outer surface of at least one bow spring. One or more of the first collar, the second collar, and the bow springs comprises a composite material. In some embodiments, the centralizer comprises a third collar, wherein the plurality of bow springs comprise a first portion of bow springs and a second portion of bow springs, and wherein the first portion of the bow springs couple the first collar to the third collar and the second portion of the bow springs couple the second collar to the third collar.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to commonly owned U.S. patent applicationSer. No. 13/013,266, entitled “Composite Bow Centralizer,” filed on Jan.25, 2011 and incorporated by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

Wellbores are sometimes drilled into subterranean formations thatcontain hydrocarbons to allow recovery of the hydrocarbons. Somewellbore servicing methods employ wellbore tubulars that are loweredinto the wellbore for various purposes throughout the life of thewellbore. Since wellbores are not generally perfectly vertical,centralizers are used to maintain the wellbore tubulars aligned withinthe wellbore. Alignment may help prevent any friction between thewellbore tubular and the side of the wellbore wall or casing,potentially reducing any damage that may occur. Common springcentralizers use stop collars located at either end of the centralizerto maintain the centralizer position relative to the wellbore tubular asthe tubular is conveyed into and out of the wellbore. The springcentralizer may be free to move within the limits of the stop collars.The spring centralizers and the stop collars are made of metals, such assteel, to provide suitable properties for the centralizer.

SUMMARY

In an embodiment, a centralizer comprises a first collar; a secondcollar; a plurality of bow springs coupling the first collar to thesecond collar; and a plurality of particulates disposed on an outersurface of at least one bow spring; wherein one or more of the firstcollar, the second collar, and the bow springs comprise a compositematerial. The leading or trailing edges of the first collar or thesecond collar may be tapered or angled. The centralizer may furthercomprise a third collar, wherein the plurality of bow springs comprise afirst portion of bow springs and a second portion of bow springs, andwherein the first portion of the bow springs couple the first collar tothe third collar and the second portion of the bow springs couple thesecond collar to the third collar. At least one of the plurality of bowsprings may have a multi-step design comprising a plurality of arcedsections. The thickness of at least one bow spring may vary along thelength of the bow spring. The particulates may comprise substantiallyspherical particles, and may have a size ranging from about 0.001 inchesto about 0.2 inches. The particulates comprise a metal or ceramic, andthe particulates comprise zirconium oxide. The particulates may becoated with a surface coating agent. The composite material may comprisea fiber and a matrix material. The matrix material may comprise a resincomprising a hardenable resin and a hardening agent. The fiber maycomprise a glass fiber, a cellulosic fiber, a carbon fiber, a graphitefiber, a metal fiber, a ceramic fiber, a metallic-ceramic fiber, anaramid fiber, or any combination thereof, and the fiber may coated witha surface coating agent.

In another embodiment, a centralizer comprises three or more collars; aplurality of bow springs comprising a plurality of portions of bowsprings, wherein each portion of bow springs couples two adjacentcollars, and wherein one or more of the collars and the bow springscomprise a composite material. The bow springs in adjacent portions maybe longitudinally aligned in an offset pattern. The number of bowsprings in a first portion and a second portion may be different. Thecentralizer may further comprise a plurality of particulates disposedalong the outer surface of at least one bow spring. The compositematerial may comprise a fiber and a matrix material. The matrix materialmay comprise a resin comprising a hardenable resin and a hardeningagent. The fiber may comprise a glass fiber, a cellulosic fiber, acarbon fiber, a graphite fiber, a metal fiber, a ceramic fiber, ametallic-ceramic fiber, an aramid fiber, or any combination thereof. Thefiber may be coated with a surface coating agent.

In an embodiment, a method comprises providing a centralizer disposedabout a wellbore tubular, wherein the centralizer comprises: a firstcollar; a second collar; a plurality of bow springs coupling the firstcollar to the second collar; and a plurality of particulates disposed onan outer surface of at least one bow spring; wherein one or more of thefirst collar, the second collar, and the bow springs comprise acomposite material; and placing the wellbore tubular in a wellboredisposed in a subterranean formation. At least one bow springs may havea multi-step design comprising a plurality of arced sections. Theparticulates may comprise substantially spherical particles, and theparticulates may comprise zirconium oxide. The particulates may becoated with a surface coating agent. The centralizer may be maintainedin position on the wellbore tubular using stop collars, protrusions,upsets, or any combination thereof. The centralizer may rotate about thewellbore tubular. The composite material may comprise a fiber and amatrix material, and the matrix material may comprise a resin comprisingat least one component selected from the group consisting of: anorthophthalic polyester, an isophthalic polyester, a phthalic/maelictype polyester, a vinyl ester, a thermosetting epoxy, a phenolic, acyanate, a bismaleimide, a nadic end-capped polyimide, a polysulfone, apolyamide, a polycarbonate, a polyphenylene oxide, a polysulfide, apolyether ether ketone, a polyether sulfone, a polyamide-imide, apolyetherimide, a polyimide, a polyarylate, a liquid crystallinepolyester, a polyurethane, a polyurea, and any combinations thereof. Thematrix material may comprise a resin comprising a hardenable resin and ahardening agent. The hardenable resin may comprise at least onecomponent selected from the group consisting of: a bisphenol Adiglycidyl ether resin, a butoxymethyl butyl glycidyl ether resin, abisphenol A-epichlorohydrin resin, a bisphenol F resin, a polyepoxideresin, a novolak resin, a polyester resin, a phenol-aldehyde resin, aurea-aldehyde resin, a furan resin, a urethane resin, a glycidyl etherresin, and any combinations thereof. The hardening agent may comprise atleast one component selected from the group consisting of: acyclo-aliphatic amine, an aromatic amine, an aliphatic amine, animidazole, a pyrazole, a pyrazine, a pyrimidine, a pyridazine, a1H-indazole, a purine, a phthalazine, a naphthyridine, a quinoxaline, aquinazoline, a phenazine, an imidazolidine, a cinnoline, an imidazoline,a 1,3,5-triazine, a thiazole, a pteridine, an indazole, an amine, apolyamine, an amide, a polyamide, a 2-ethyl-4-methyl imidazole, and anycombinations thereof. The fiber may coated with a surface coating agent,and the surface coating agent may comprise at least one compoundselected from the group consisting of: a silazane, a siloxane, analkoxysilane, an aminosilane, a silane, a silanol, a polyvinyl alcohol,and any combination thereof.

In still another embodiment, a method comprises providing a centralizerdisposed about a wellbore tubular, wherein the wellbore tubularcomprises a stop collar, a protrusion, or an upset on either end of thecentralizer, and wherein the centralizer comprises: three or morecollars; a plurality of bow springs comprising a plurality of portionsof bow springs, wherein each portion of bow springs couples two adjacentcollars, and wherein one or more of the collars and the bow springscomprise a composite material; and placing the wellbore tubular in awellbore disposed in a subterranean formation. The bow springs in atleast two adjacent portions may be longitudinally aligned in an offsetpattern. The method may further comprises a plurality of particulatesdisposed along an outer surface of at least one bow spring. Thecomposite material may comprise a fiber and a matrix material. Thematrix material may comprise a resin comprising a hardenable resin and ahardening agent. The fiber may be coated with a surface coating agent,and the surface coating agent may comprise at least one compoundselected from the group consisting of: a silazane, a siloxane, analkoxysilane, an aminosilane, a silane, a silanol, a polyvinyl alcohol,and any combination thereof.

In an embodiment, a centralizer is produced from a process comprising:forming a plurality of composite bow spring from a fiber and a resin;disposing a plurality of particulates on an outer surface of thecomposite bow springs; curing the composite bow springs in a desiredshape to form a plurality of cured bow springs; disposing a firstportion of a resin-wetted fiber about a cylindrical mandrel to form aplurality of collars; disposing the plurality of cured bow springs ontothe mandrel with the bow spring ends in contact with the first portionof resin-wetted fiber; disposing a second portion of the resin-wettedfiber about the cylindrical mandrel; curing the collars to form a curedcentralizer; and pressing the mandrel out of the cured centralizer. Thefiber may be supplied as a filament, a yarn, a tow, a roving, a tape, afabric, or any combination thereof. The fiber in the composite bowspring may be aligned in a longitudinal direction, and the fiber in thecollars may be aligned in a circumferential direction. The process maycomprise an automated process, and the automated process may consider adiameter of the fiber, a stiffness of the fiber, a moduli of the fiber,a cost of the fiber, or any combination thereof.

These and other features will be more clearly understood from thefollowing detailed description taken in conjunction with theaccompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and theadvantages thereof, reference is now made to the following briefdescription, taken in connection with the accompanying drawings anddetailed description:

FIG. 1 is a cut-away view of an embodiment of a wellbore servicingsystem according to an embodiment.

FIG. 2 is a plan view of a centralizer according to an embodiment.

FIGS. 3A and 3B are plan views of centralizers according to embodiments.

FIGS. 4A, 4B, and 4C are cross-sectional views of centralizerscomprising bow springs according to other embodiments.

FIG. 5 is a plan view of a centralizer according to yet anotherembodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the drawings and description that follow, like parts are typicallymarked throughout the specification and drawings with the same referencenumerals, respectively. The drawing figures are not necessarily toscale. Certain features of the invention may be shown exaggerated inscale or in somewhat schematic form and some details of conventionalelements may not be shown in the interest of clarity and conciseness.

Unless otherwise specified, any use of any form of the terms “connect,”“engage,” “couple,” “attach,” or any other term describing aninteraction between elements is not meant to limit the interaction todirect interaction between the elements and may also include indirectinteraction between the elements described. In the following discussionand in the claims, the terms “including” and “comprising” are used in anopen-ended fashion, and thus should be interpreted to mean “including,but not limited to . . . ”. Reference to up or down will be made forpurposes of description with “up,” “upper,” “upward,” or “upstream”meaning toward the surface of the wellbore and with “down,” “lower,”“downward,” or “downstream” meaning toward the terminal end of the well,regardless of the wellbore orientation. The various characteristicsmentioned above, as well as other features and characteristics describedin more detail below, will be readily apparent to those skilled in theart with the aid of this disclosure upon reading the following detaileddescription of the embodiments, and by referring to the accompanyingdrawings.

Disclosed herein is a centralizer for use with a wellbore tubular. Thecentralizer may comprise one or more composite materials. The resultingcentralizer may be relatively light weight as compared to a traditionalmetallic centralizer, representing an operational safety advantage. Theuse of composite materials may allow for an easier and faster removal ofthe centralizer and/or any centralizer components from the wellboreshould a centralizer fail within the wellbore as compared to metalliccentralizers and/or metallic centralizer components. Further, thecomposite materials may allow for the use of the centralizers inmagnetically sensitive applications (e.g., measurement while drillingsubs, surveying, etc.). In addition, the ability to form thecentralizers from a composite material may allow the centralizer to bequickly manufactured and tailored to a particular application, which mayallow a centralizer to be optimized for a given use based on theconditions in a specific wellbore. Further, the ability to use variousmaterials of construction such as various fibers, resins, and/orparticulates may allow for a flexible design, cost effectiveness, andgeometry previously unavailable with traditional metallic centralizers.

Referring to FIG. 1, an example of a wellbore operating environment isshown. As depicted, the operating environment comprises a drilling rig106 that is positioned on the earth's surface 104 and extends over andaround a wellbore 114 that penetrates a subterranean formation 102 forthe purpose of recovering hydrocarbons. The wellbore 114 may be drilledinto the subterranean formation 102 using any suitable drillingtechnique. The wellbore 114 extends substantially vertically away fromthe earth's surface 104 over a vertical wellbore portion 116, deviatesfrom vertical relative to the earth's surface 104 over a deviatedwellbore portion 136, and transitions to a horizontal wellbore portion118. In alternative operating environments, all or portions of awellbore may be vertical, deviated at any suitable angle, horizontal,and/or curved. The wellbore may be a new wellbore, an existing wellbore,a straight wellbore, an extended reach wellbore, a sidetracked wellbore,a multi-lateral wellbore, and other types of wellbore for drilling andcompleting one or more production zones. Further the wellbore may beused for both producing wells and injection wells. In an embodiment, thewellbore may be used for purposes other than or in addition tohydrocarbon production, such as uses related to geothermal energy.

A wellbore tubular string 120 comprising a centralizer 200 may belowered into the subterranean formation 102 for a variety of drilling,completion, workover, or treatment procedures throughout the life of thewellbore. The embodiment shown in FIG. 1 illustrates the wellboretubular 120 in the form of a casing string being lowered into thesubterranean formation. It should be understood that the wellboretubular 120 comprising a centralizer 200 is equally applicable to anytype of wellbore tubular being inserted into a wellbore, including asnon-limiting examples liners, drill pipe, production tubing, rodstrings, and coiled tubing. The centralizer 200 may also be used tocentralize various subs and workover tools. In the embodiment shown inFIG. 1, the wellbore tubular 120 comprising centralizer 200 is conveyedinto the subterranean formation 102 in a conventional manner and maysubsequently be secured within the wellbore 114 by filling an annulus112 between the wellbore tubular 120 and the wellbore 114 with acementitous material.

The drilling rig 106 comprises a derrick 108 with a rig floor 110through which the wellbore tubular 120 extends downward from thedrilling rig 106 into the wellbore 114. The drilling rig 106 comprises amotor driven winch and other associated equipment for extending thecasing string 120 into the wellbore 114 to position the wellbore tubular120 at a selected depth. While the operating environment depicted inFIG. 1 refers to a stationary drilling rig 106 for lowering and settingthe wellbore tubular 120 comprising the centralizer 200 within aland-based wellbore 114, in alternative embodiments, mobile workoverrigs, wellbore servicing units (such as coiled tubing units), and thelike may be used to lower the wellbore tubular 120 comprising thecentralizer 200 into a wellbore. It should be understood that a wellboretubular 120 comprising the centralizer 200 may alternatively be used inother operational environments, such as within an offshore wellboreoperational environment.

In alternative operating environments, a vertical, deviated, orhorizontal wellbore portion may be cased and cemented and/or portions ofthe wellbore may be uncased. For example, uncased section 140 maycomprise a section of the wellbore 114 ready for being cased withwellbore tubular 120. In an embodiment, the centralizer may be disposedon production tubing in a cased or uncased well. In an embodiment, aportion of the wellbore 114 may comprise an underreamed section. As usedherein, underreaming refers to the enlargement of an existing wellborebelow an existing section, which may be cased in some embodiments. Anunderreamed section may have a larger diameter than a section upwardfrom the underreamed section. Thus, a wellbore tubular passing downthrough the wellbore may pass through a smaller diameter passagefollowed by a larger diameter passage.

Regardless of the type of operational environment the centralizer 200 isused, it will be appreciated that the centralizer 200 serves to aid inguiding and placing the wellbore tubular 120 through the wellbore 114.As described in greater detail below, the centralizer 200 comprisescollars 202, 204, and a plurality of bow springs 206 connecting thecollars 202, 204. The centralizer serves to center the wellbore tubular(e.g., casing string 120) within the wellbore 114 as the wellboretubular 120 is conveyed within the wellbore 114.

Several forces are used to characterize centralizers 200. The bowsprings 206 provide a force known as a “restoring force” to radially(i.e., laterally) urge the wellbore tubular away from the wall of thewellbore. At the same time, the bow springs 206 may be laterallycompressible so that the wellbore tubular may be moved along theinterior of the wellbore notwithstanding the presence in the wellbore ofsmall diameter restrictions and other obstacles to longitudinal movementof the wellbore tubular within the wellbore. Upon encountering arestriction within the wellbore during conveyance, the bow springs maybe compressed in order to enter the restriction. The force required tocompress the bow springs and insert the centralizer into the interior ofthe restriction, which may include the initial insertion into thewellbore, is referred to as the “starting force.” The contact betweenthe bow springs and the wall of the wellbore may lead to a drag force.The force required to overcome the drag force may be referred to as the“running force,” which is the amount of force required to move thewellbore tubular longitudinally along the wellbore with the centralizeraffixed to its exterior. Specifications for the amount of restoringforce and proper use of centralizers are described in a documententitled, Specifications for Bow-Spring Centralizers, API Specification10D, 5th edition, American Petroleum Institute, Washington, D.C. (1994),which is incorporated herein by reference in its entirety. Generallyspeaking, casing centralizers are made to center a particular outsidediameter (OD) wellbore tubular within a particular nominal diameterwellbore or outer wellbore tubular (e.g., a casing).

Referring now to FIG. 2, an embodiment of the centralizer 200 is shownin greater detail. As described above, the centralizer 200 comprisesfirst collar 202, second collar 204, and a plurality of bow springs 206connecting the collars 202, 204. The collars 202, 204 and the pluralityof bow springs 206 may be formed from steel, a composite, or any othersimilar high strength material. In an embodiment, the collars 202, 204,and/or the bow springs 206 may be made from a composite material. Thecollars 202, 204 may be generally cylindrical in shape and may have aninternal diameter selected to be disposed about the exterior of awellbore tubular to which they are to be coupled. The collars 202, 204may have a desired length 210, 212 based on the mechanical requirementsof the of the centralizer 200 and taking into account the material ofconstruction and the length necessary to integrate the bow springs 206,as described in more detail below. As used herein, the length of thecentralizer and/or one or more bow springs refers to the dimension ofthe centralizer 200 in the longitudinal direction of the wellboretubular 120, and the width of the centralizer 200 and/or one or more bowsprings 206 refers to the dimension in a direction perpendicular to thelongitudinal direction of the wellbore tubular 120 along the surface ofthe wellbore tubular 120. In an embodiment the length 210 of the firstcollar 202 and the length 212 of the second collar 204 may be the sameor different. The leading and/or trailing edges 214, 216 of the firstcollar 202 and/or the second collar 204 may be tapered or angled to aidin movement of the centralizer 200 through the wellbore (e.g., through arestriction and/or upon entering the wellbore). In an embodiment, whenstop collars are used to maintain the centralizer 200 in position on thewellbore tubular, the leading and/or trailing edges of the stop collarsmay be tapered and the leading and/or trailing edges 214, 216 may not betapered.

In an embodiment shown in FIG. 3A, a multi-section centralizer design isshown with a third collar 302 disposed between the first collar 202 andthe second collar 204. A first portion 304 of a plurality of bow springsmay be used to couple the first collar 202 and the third collar 302, anda second portion 306 of the plurality of bow springs may be used tocouple the third collar 502 and the second collar 204. The third collar302 may be similar in design to the collars 202, 204. The collars 202,204, 302 and any of the bow spring portions 304, 306 may be formed fromsteel, a composite, or any other similar high strength material. In anembodiment, one or more of the first collar 202, the second collar 204,the third collar 302, the first portion 304 of the plurality of bowsprings, and the second portion 306 of the plurality of bow springs maycomprise a composite material. The first portion 304 of the bow springsand the second portion 306 of the bow springs may be coupled to thethird collar 302 using any of the means disclosed herein. As shown inFIG. 3A, the number of bow springs in the first portion 304 and thesecond portion 306 of bow springs may be the same, and the bow springsin each portion may be aligned along the longitudinal axis of thewellbore tubular. In another embodiment as shown in FIG. 3B, the numberof bow springs in the first portion 306 and the second portion 304 ofbow springs may be the same, and the bow springs in each portion may beoffset so that the bow springs do not align along the longitudinal axisof the wellbore tubular 120. In another embodiment, the number of bowsprings in the first portion and the second portion of bow springs maybe different, and the bow springs in each portion may be offset so thatthe bow springs do not align. For example, the first portion may have 5bow springs and the second portion may have 3 bow springs. In thisexample, the bow springs in the first portion and the second portion maybe aligned so that none of the bow springs in the first portion alignalong the longitudinal axis of the wellbore tubular 120 with any of thebow springs in the second portion. In an embodiment, the use of multiplecollars to allow for additional bow springs between the first collar 202and the second collar 204 may increase the restoring force without acorresponding increase in the starting force, allowing for the desiredproperties to be tailored based on the design of the centralizer 200. Asa further advantage, a design in which the bow springs in each portionare arranged in a longitudinally offset alignment may allow for therestoring force to be increased without an increase in the startingforce.

It will be appreciated that while a third collar 302 is illustrated, anynumber of additional collars may be disposed between subsequent portionsof the bow springs to connect the first collar 202 to the second collar204. In an embodiment, a plurality of collars may be coupled by aplurality of portions of bow springs. Further, the plurality of sectionsmay each have the same number of bow springs or a different number ofbow springs, and the bow springs in each portion may be aligned along alongitudinal axis or offset with respect to the longitudinal axis. Whilea single section is described below for clarity, it is to be understoodthat the same concepts may be readily applied by one of ordinary skillin the art to a multi-section design.

Returning to FIG. 2, a plurality of bow springs 206 may connect thecollars 202, 204, and optionally one or more interior collars in amulti-section design. The bow springs 206 may be formed from a compositematerial comprising the same components as the first collar 202 and/orthe second collar 204 or different composite materials from the firstcollar 202 and/or the second collar 204. In an embodiment, one or moreof the bow springs may be formed from steel or a similar high strengthmaterial. Two or more bow springs 206 may be used to couple the collars202, 204. The number of bow springs 206 may be chosen based on thewellbore tubular properties (e.g., weight, size), the wellboreproperties (e.g., orientation, tortuosity, etc.), the wellbore serviceconditions (e.g., temperature, acidity, etc.) and/or the annulardistance available between the wellbore tubular and the inner wellborewall. The number of bow springs 206 may also be chosen to reduce thestarting and/or drag forces while increasing the restoring forceavailable within the wellbore. The bow springs 206 may generally extendlongitudinally between the collars 202, 204. However, additionalorientations may be used depending on the desired use of thecentralizer. For example, helical and/or angled orientations are alsopossible. Each of the bow springs 206 may comprise the same materialsand orientation. In an embodiment, each bow spring or any combination ofthe plurality of bow springs may comprise different materials andorientations.

The bow springs 206 may generally have an arced profile between thecollars 202, 204, though any suitable shape (e.g., recurved) imparting astandoff from the wellbore tubular and a desired restoring force may beused. In an embodiment shown in FIG. 4A, the bow springs 206 may have asmooth arc between the collars 202, 204. The spring force providing therestoring force may then be described by known spring equations. In anembodiment shown in FIG. 4B and FIG. 4C, the bow springs 206 may have amulti-step design. In this embodiment, the bow springs may general havea first arced section 402 between the collars 202, 204 with a secondarced section 404 disposed along the length of the bow spring betweenthe collars 202, 204. The second arced section 404 may be formed in avariety of shapes, (e.g., an arc of increased angle, a sinusoidal curve,etc.). The second arced section 404 may generally have an increasedspring constant for imparting an increased restoring force to the bowspring. As a result of the multi-step design, the restoring force mayincrease in steps as the bow spring 206 is displaced in a radialdirection towards the center of the centralizer 200. The initialdisplacement may occur as a result of the flexing of the larger arcedsection 402 as shown in FIG. 4C. Additional inward displacement maycause the second arced section 404 to flex and present a greaterrestoring force. In an embodiment, a plurality of arced sections couldbe implemented along a bow spring 206 to create a restoring forceprofile as desired. In an embodiment, each of the bow springs 206 maycomprise the same shape. In another embodiment, each bow spring or anycombination of the plurality of bow springs may comprise differentshapes.

The restoring force may also be tailored based on additionalconsiderations including, but not limited to, the thickness of a bowspring and/or the width of a bow spring. A bow spring may have a uniformthickness along the length of the bow spring, or the thickness may varyalong the length of the bow spring. As shown in FIG. 4A, the thickness406 of the bow spring 206 may be substantially uniform along the lengthof the bow spring 206. As used herein, “substantially uniform” refers toa thickness that may vary within the manufacturing tolerances of thecomponent. In an embodiment shown in FIG. 4B and FIG. 4C, the thickness410 of the first arced section 402 may be less than the thickness 408 ofthe second arced section 404. In general, the restoring force mayincrease as the thickness of the bow spring increases. Similarly, therestoring force may increase as the width of the bow spring increases.The thickness, width, and length may be limited based upon thecharacteristics of the wellbore tubular and the wellbore into which thecentralizer is disposed. Further design factors that may affect therestoring force, the starting force, and the running force may include,but are not limited to, the type of fiber or fibers used in forming thebow springs, and/or the type of matrix material or materials used toform the bow springs, each of which are discussed in more detail below.Still further design factors may include the angle of winding of thefibers and the thickness of the fibers.

Referring again to FIG. 2, the bow springs may have a plurality ofparticulates 220 disposed on the outer surface of the bow springs 206.As used herein, the “outer surface” of the bow springs 206 comprisesthose portions of the bow springs anticipated to contact a surface of awellbore and/or tubular into which the centralizer is placed. Theparticulates may be disposed along the entire length of the bow springsor only those portions anticipated to contact the wellbore wall duringconveyance of the centralizer and wellbore tubular within the wellbore.As used herein, disposed on the outer surface generally refers to theparticulates being located at the outer surface of the bow springs 206and may include the particulates being embedded in the outer surface,deposited in and/or on the outer surface, and/or coated on the outersurface. The particulates may generally be resistant to erosion and/orabrasion to prevent wear on the points of contact between the bow springsurfaces and the wellbore walls or inner surfaces of the wellbore. Theshape, size, and composition of the particulates may be selected toaffect the amount of friction between the bow springs and the wellborewalls during conveyance of the wellbore tubular comprising thecentralizer within the wellbore. In general, the particulates may beselected to reduce the running forces required during conveyance of thewellbore tubular within the wellbore. In an embodiment, the particulatesmay comprise a low surface energy and or coefficient of friction, and/ormay comprise substantially spherical particles. The particulates mayhave a distribution of sizes, or they may all be approximately the samesize. In an embodiment, the particulates may be within a distribution ofsizes ranging from about 0.001 inches to about 0.2 inches, 0.005 inchesto about 0.1 inches, 0.01 inches to about 0.005 inches. In anembodiment, the particulates may be about 0.02 inches to about 0.004inches. The particulates may comprise any material capable of resistingabrasion and erosion when disposed on a bow spring and contacted withthe wellbore wall. In an embodiment, the particulates may be formed frommetal and/or ceramic. For example, the particulates may comprisezirconium oxide. In an embodiment, the particulates may be coated withany of the surface coating agents discussed below to aid in bondingbetween the particulates and one or more materials of construction ofthe centralizer or any centralizer components.

The centralizer 200 may be disposed about a wellbore tubular 120 andmaintained in place using any technique known in the art. In anembodiment as shown in FIG. 5, stop collars 502, 504 may be used toretain the centralizer 200 on a wellbore tubular 120. The stop collars502, 504 may be made from steel or similar high strength material. In anembodiment, the stop collars 502, 504 may be constructed from acomposite material. The stop collars 502, 504 may be generallycylindrically shaped and may have an internal diameter selected to fitabout the exterior of the wellbore tubular 120 to which they are to beaffixed. The stop collars 502, 504 may be affixed to the exterior of thewellbore tubular using set screws 506 or any other device known in theart for such purpose. In an embodiment, the stop collars may beconstructed of a composite material and may take the form of any of thestop collars shown in U.S. Patent Application Publication Nos. US2005/0224123 A1, entitled “Integral Centraliser” and published on Oct.13, 2005, and US 2007/0131414 A1, entitled “Method for MakingCentralizers for Centralising a Tight Fitting Casing in a Borehole” andpublished on Jun. 14, 2007, both of which are incorporated herein byreference in their entirety. The use of stop collars 502, 504 may allowthe centralizer 200 to rotate with respect to the wellbore tubular 120as the centralizer 200 may not be fixedly coupled to the wellboretubular 120. In an embodiment, a friction device or connector (e.g., aset screw in one or more of the collars 202, 204) may be used to fixedlyconnect the centralizer 200 to the wellbore tubular 120. In anembodiment, the friction device or connector may be formed from acomposite material.

Additional connection methods may be used to couple the centralizer tothe wellbore tubular. In an embodiment, a projection may be formed onthe wellbore tubular using a composite material that is capable ofretaining the centralizer 200 on the wellbore tubular. Suitableprojections and methods of making the same are disclosed in U.S. PatentApplication Publication No. 2005/0224123 A1 to Baynham et al. andpublished on Oct. 13, 2005, the entire disclose of which is incorporatedherein by reference. The projections may comprise a composite material,which may comprise a ceramic based resin including, but not limited to,the types disclosed in U.S. Patent Application Publication Nos. US2005/0224123 A1, entitled “Integral Centraliser” and published on Oct.13, 2005, and US 2007/0131414 A1, entitled “Method for MakingCentralizers for Centralising a Tight Fitting Casing in a Borehole” andpublished on Jun. 14, 2007, both of which were incorporated by referenceabove. In another embodiment as shown in the centralizer 200 of FIG. 1,at least one window may be disposed in a collar 202, 204, and may beused to couple the centralizer 200 to a wellbore tubular 120. The windowdisposed in a collar 202, 204 may comprise a cutout of the collar 202,204 that allows for access through the collar 202, 204. An upset may becreated within the window to couple the centralizer 200 to the wellboretubular 120. Suitable configurations, materials, and methods of couplingthe centralizer 200 to the wellbore tubular 120 using a window with anupset disposed therein are disclosed in co-pending U.S. patentapplication Ser. No. 12/964,605, filed on Dec. 9, 2010, and entitled“Integral Pull-Through Centralizer,” the entire disclosure of which isincorporated herein by reference.

Referring to FIG. 5, the stop collars 502, 504 or other means ofretaining the centralizer 200 on the wellbore tubular 120 may besufficiently spaced apart to allow the centralizer 200 to expandlongitudinally when radially compressed. The radial, inward compressionof the bow springs 206 creates a longitudinal lengthening of thedistance 514 between the collars 202, 204, thus increasing the overalllength of the centralizer 200. The increase in length of the centralizer200 is approximately the same as or greater than the radial distance 508traveled by bow spring 206 during the compression. In order toaccommodate this longitudinal travel, the stop collars 502, 504 may bespaced so that the sum of the distances 510 and 512 are equal to orgreater than the greatest radial travel distance 508 of the plurality ofbow springs 206. In an embodiment, the sum of the distances 510 and 512may be about 5% to about 10% greater than the distance 508 to allow foroperational tolerances during coupling of the centralizer 200 to thewellbore tubular 120 using the stop collars 502, 504.

The centralizer 200 may be formed from one or more composite materials.A composite material comprises a heterogeneous combination of two ormore components that differ in form or composition on a macroscopicscale. While the composite material may exhibit characteristics thatneither component possesses alone, the components retain their uniquephysical and chemical identities within the composite. Compositematerials may include a reinforcing agent and a matrix material. In afiber-based composite, fibers may act as the reinforcing agent. Thematrix material may act to keep the fibers in a desired location andorientation and also serve as a load-transfer medium between fiberswithin the composite.

The matrix material may comprise a resin component, which may be used toform a resin matrix. Suitable resin matrix materials that may be used inthe composite materials described herein may include, but are notlimited to, thermosetting resins including orthophthalic polyesters,isophthalic polyesters, phthalic/maelic type polyesters, vinyl esters,thermosetting epoxies, phenolics, cyanates, bismaleimides, nadicend-capped polyimides (e.g., PMR-15), and any combinations thereof.Additional resin matrix materials may include thermoplastic resinsincluding polysulfones, polyamides, polycarbonates, polyphenyleneoxides, polysulfides, polyether ether ketones, polyether sulfones,polyamide-imides, polyetherimides, polyimides, polyarylates, liquidcrystalline polyester, polyurethanes, polyureas, and any combinationsthereof.

In an embodiment, the matrix material may comprise a two-component resincomposition. Suitable two-component resin materials may include ahardenable resin and a hardening agent that, when combined, react toform a cured resin matrix material. Suitable hardenable resins that maybe used include, but are not limited to, organic resins such asbisphenol A diglycidyl ether resins, butoxymethyl butyl glycidyl etherresins, bisphenol A-epichlorohydrin resins, bisphenol F resins,polyepoxide resins, novolak resins, polyester resins, phenol-aldehyderesins, urea-aldehyde resins, furan resins, urethane resins, glycidylether resins, other epoxide resins, and any combinations thereof.Suitable hardening agents that can be used include, but are not limitedto, cyclo-aliphatic amines; aromatic amines; aliphatic amines;imidazole; pyrazole; pyrazine; pyrimidine; pyridazine; 1H-indazole;purine; phthalazine; naphthyridine; quinoxaline; quinazoline; phenazine;imidazolidine; cinnoline; imidazoline; 1,3,5-triazine; thiazole;pteridine; indazole; amines; polyamines; amides; polyamides;2-ethyl-4-methyl imidazole; and any combinations thereof. In anembodiment, one or more additional components may be added the matrixmaterial to affect the properties of the matrix material. For example,one or more elastomeric components (e.g., nitrile rubber) may be addedto increase the flexibility of the resulting matrix material.

The fibers may lend their characteristic properties, including theirstrength-related properties, to the composite. Fibers useful in thecomposite materials used to form a collar and/or one or more bow springsmay include, but are not limited to, glass fibers (e.g., e-glass,A-glass, E-CR-glass, C-glass, D-glass, R-glass, and/or S-glass),cellulosic fibers (e.g., viscose rayon, cotton, etc.), carbon fibers,graphite fibers, metal fibers (e.g., steel, aluminum, etc.), ceramicfibers, metallic-ceramic fibers, aramid fibers, and any combinationsthereof.

The strength of the interface between the fibers and the matrix materialmay be modified or enhanced through the use of a surface coating agent.The surface coating agent may provide a physico-chemical link betweenthe fiber and the resin matrix material, and thus may have an impact onthe mechanical and chemical properties of the final composite. Thesurface coating agent may be applied to fibers during their manufactureor any other time prior to the formation of the composite material.Suitable surface coating agents may include, but are not limited to,surfactants, anti-static agents, lubricants, silazane, siloxanes,alkoxysilanes, aminosilanes, silanes, silanols, polyvinyl alcohol, andany combinations thereof.

A centralizer comprising a composite material may be formed using anytechniques known for forming a composite material into a desired shape.The fibers used in the process may be supplied in any of a number ofavailable forms. For example, the fibers may be supplied as individualfilaments wound on bobbins, yarns comprising a plurality of fibers woundtogether, tows, rovings, tapes, fabrics, other fiber broadgoods, or anycombinations thereof. The fiber may pass through any number rollers,tensioners, or other standard elements to aid in guiding the fiberthrough the process to a resin bath.

In an embodiment, a fiber may first be delivered to a resin bath. Theresin may comprise any of those resins or combination of resins known inthe art, including those listed herein. The resin bath can beimplemented in a variety of ways. For example, the resin bath maycomprise a doctor blade roller bath wherein a polished rotating cylinderthat is disposed in the bath picks up resin as it turns. The doctor barpresses against the cylinder to obtain a precise resin film thickness oncylinder and pushes excess resin back into the bath. As the fiber passesover the top of the cylinder and is in contact with the cylinder, thefiber may contact the resin film and wet out. In another embodiment,resin bath may comprise an immersion bath where the fiber is partiallyor wholly submerged into the resin and then pulled through a set ofwipers or roller that remove excess resin.

After leaving the resin bath, the resin-wetted fiber may pass throughvarious rings, eyelets, and/or combs to direct the resin-wetted fiber toa mandrel to form the bow springs. The fibers may be wound onto themandrel to form the base for the bow springs using an automated processthat may allow for control of the direction of the winding and thewinding pattern. The winding process may determine the thickness profileof the bow springs in the bow spring formation process. In anembodiment, particulates, which may comprise a surface coating agent,may be disposed on the outer surface of the bow springs after the fibersleave the resin bath and/or when disposed on the mandrel.

The wound fibers may be allowed to harden or set to a desired degree onthe mandrel before being cut and removed from the mandrel as a mat. Themat may then be divided into strips of a desired dimension to initiallyform the bow springs. The strips may be placed in a shaped mold to curein a desired shape. In an embodiment the mold may comprise a two-pieceblock mold in which one or more of the strips are placed and formed intoa desired shape due to the form of the two piece mold. In an embodiment,the particulates, which may comprise a surface coating agent, may bedisposed on the outer surface of the bow springs when the bow springsare placed in the mold. The mold may then be heated to heat cure theresin to a final, cured state. In another embodiment, other curingtechniques may be used to cause the strips to harden to a final, curedstate. After completing the curing process, the mold may be disassembledand the bow springs removed.

One or more collars may then be prepared according to a similar process.The fiber and/or combination of fibers used to form one or more collarsmay be passed through a resin bath as described above. The resin-wettedfibers may then be wound onto a cylindrical mandrel of a desired shape,which may be the same or different than the cylindrical mandrel used toform the bow springs. In an embodiment, the cylindrical mandrel uponwhich the resin-wetted collar fibers are wound may have a diameterapproximately the same as the diameter of a wellbore tubular upon whichthe final centralizer is to be disposed. The fibers may be wound ontothe cylindrical mandrel to form a portion of the collars using anautomated process that may allow for control of the direction of thewinding and the winding pattern. After winding a portion of theresin-wetted collar fibers onto the cylindrical mandrels, the bowsprings may be placed onto the cylindrical mandrel in the desiredpositions. The bow springs may be held in place using temporaryrestraining means (e.g., tape), or the resin used on the collar fibersmay be sufficiently tacky to hold the bow springs in place during theremainder of the manufacturing process.

Additional resin-wetted collar fibers may then be wound onto thecylindrical mandrel, at least a portion of which may be placed on top ofthe ends of the bow springs. In this manner, the bow springs may beintegrally formed into the collars. The fibers may be wound onto thecylindrical mandrel to form the remainder of the collars using anautomated process that may allow for control of the direction of thewinding and the winding pattern. The formed centralizer may then becured to produce a final, cured state in the collars and the bowsprings. In an embodiment, a heat cycle may be used to thermally cure athermally curable resin, and/or any other number of curing processes maybe used to cure an alternative or additional resin used in the formationof the composite centralizer. The cylindrical mandrel may then bepressed out of the centralizer. In an embodiment, the centralizer maythen be disposed about a wellbore tubular and secured in place using anyof the methods disclosed above.

The winding process used to form the bow springs and/or the collars maydetermine the direction of the fibers and the thickness of the bowsprings and/or collars. The ability to control the direction and patternof winding may allow for the properties of the completed centralizerand/or centralizer components to possess direction properties. In anembodiment, the direction of the fibers in the collars may be differentthan the direction of the fibers in the bow springs. In an embodiment,the fibers in the collars may generally be aligned in a circumferentialdirection, and the fibers in the bow springs may generally be alignedalong the longitudinal axis of the centralizer.

In an embodiment, the centralizer formation process may be designed byand/or controlled by an automated process, which may be implemented assoftware operating on a processor. The automated process may considervarious desired properties of the centralizer as inputs and calculate adesign of the centralizer based on the properties of the availablematerials and the available manufacturing processes. In an embodiment,the automated process may consider various properties of the materialsavailable for use in the construction of the centralizer including, butnot limited to, the diameter, stiffness, moduli, and cost of the fibers.The desired properties of the centralizer may comprise the geometry ofthe centralizer, the restoring force, the running force, the startingforce, and any other specific considerations such as a desired choice ofmaterials. The use of the automated process may allow for centralizersto be designed for specific uses and allow the most cost effectivedesign to be chosen at the time of manufacture. Thus, the ability totailor the design of the centralizer to provide a desired set ofproperties may offer an advantage of the centralizer and methodsdisclosed herein.

In an embodiment, a plurality of centralizers may be used with one ormore wellbore tubular sections. A wellbore tubular string refers to aplurality of wellbore tubular sections connected together for conveyancewithin the wellbore. For example, the wellbore tubular string maycomprise a casing string conveyed within the wellbore for cementing. Thewellbore casing string may pass through the wellbore prior to the firstcasing string being cemented, or the casing string may pass through oneor more casing strings that have been cemented in place within thewellbore. A plurality of centralizers as described herein may be used onthe wellbore tubular string to centralize the wellbore tubular string asit is conveyed within the wellbore. The number of centralizers and theirrespective spacing along a wellbore tubular string may be determinedbased on a number of considerations including the properties of eachcentralizer (e.g., the restoring force, the starting force, the runningforce, etc.), the properties of the wellbore tubular (e.g., the sizing,the weight, etc.), and the properties of the wellbore through which thewellbore tubular is passing (e.g., the annular diameter difference, thetortuosity, the orientation of the wellbore, etc.). In an embodiment, awellbore design program may be used to determine the number and type ofthe centralizers based on the various inputs as described herein. Thewellbore design program may be coupled with the automated centralizerdesign process to produce a plurality of centralizers tailored to theconditions that each section of wellbore tubular may encounter in therespective section of the wellbore. The number of centralizers and thespacing of the centralizers along the wellbore tubular may vary alongthe length of the wellbore tubular based on the expected conditionswithin the wellbore.

At least one embodiment is disclosed and variations, combinations,and/or modifications of the embodiment(s) and/or features of theembodiment(s) made by a person having ordinary skill in the art arewithin the scope of the disclosure. Alternative embodiments that resultfrom combining, integrating, and/or omitting features of theembodiment(s) are also within the scope of the disclosure. Wherenumerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example,whenever a numerical range with a lower limit, R₁, and an upper limit,R_(u), is disclosed, any number falling within the range is specificallydisclosed. In particular, the following numbers within the range arespecifically disclosed: R=R₁+k*(R_(u)-R₁), wherein k is a variableranging from 1 percent to 100 percent with a 1 percent increment, i.e.,k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97percent, 98 percent, 99 percent, or 100 percent. Moreover, any numericalrange defined by two R numbers as defined in the above is alsospecifically disclosed. Use of the term “optionally” with respect to anyelement of a claim means that the element is required, or alternatively,the element is not required, both alternatives being within the scope ofthe claim. Use of broader terms such as comprises, includes, and havingshould be understood to provide support for narrower terms such asconsisting of, consisting essentially of, and comprised substantiallyof. Accordingly, the scope of protection is not limited by thedescription set out above but is defined by the claims that follow, thatscope including all equivalents of the subject matter of the claims.Each and every claim is incorporated as further disclosure into thespecification and the claims are embodiment(s) of the present invention.

Reference is further made to the following specific embodiments:

-   1. A centralizer comprising:    -   a first collar;    -   a second collar;    -   a plurality of bow springs coupling the first collar to the        second collar; and    -   a plurality of particulates disposed on an outer surface of at        least one bow spring;    -   wherein one or more of the first collar, the second collar, and        the bow springs comprise a composite material.-   2. The centralizer of embodiment 1, wherein the leading or trailing    edges of the first collar or the second collar are tapered or    angled.-   3. The centralizer of embodiment 1, wherein the centralizer further    comprises a third collar, wherein the plurality of bow springs    comprise a first portion of bow springs and a second portion of bow    springs, and wherein the first portion of the bow springs couple the    first collar to the third collar and the second portion of the bow    springs couple the second collar to the third collar.-   4. The centralizer of embodiment 1, wherein at least one bow spring    has a multi-step design comprising a plurality of arced sections.-   5. The centralizer of embodiment 1, wherein the thickness of at    least one bow spring varies along the length of the bow spring.-   6. The centralizer of embodiment 1, wherein the particulates    comprise substantially spherical particles.-   7. The centralizer of embodiment 1, wherein the particulates have a    size ranging from about 0.001 inches to about 0.2 inches.-   8. The centralizer of embodiment 1, wherein the particulates    comprise a metal or ceramic.-   9. The centralizer of embodiment 1, wherein the particulates    comprise zirconium oxide.-   10. The centralizer of embodiment 1, wherein the particulates are    coated with a surface coating agent.-   11. The centralizer of embodiment 1, wherein the composite material    comprises a fiber and a matrix material.-   12. The centralizer of embodiment 11, wherein the matrix material    comprises a resin comprising a hardenable resin and a hardening    agent.-   13. The centralizer of embodiment 11, wherein the fiber comprise a    glass fiber, a cellulosic fiber, a carbon fiber, a graphite fiber, a    metal fiber, a ceramic fiber, a metallic-ceramic fiber, an aramid    fiber, or any combination thereof.-   14. The centralizer of embodiment 11, wherein the fiber is coated    with a surface coating agent.-   15. A centralizer comprising:    -   three or more collars;    -   a plurality of bow springs comprising a plurality of portions of        bow springs, wherein each portion of bow springs couples two        adjacent collars, and wherein one or more of the collars and the        bow springs comprise a composite material.-   16. The centralizer of embodiment 15, wherein the bow springs in    adjacent portions are longitudinally aligned in an offset pattern.-   17. The centralizer of embodiment 15, wherein the number of bow    springs in a first portion and a second portion are different.-   18. The centralizer of embodiment 15, further comprising a plurality    of particulates disposed along the outer surface of at least one bow    spring.-   19. The centralizer of embodiment 15, wherein the composite material    comprises a fiber and a matrix material.-   20. The centralizer of embodiment 19, wherein the matrix material    comprises a resin comprising a hardenable resin and a hardening    agent.-   21. The centralizer of embodiment 19, wherein the fiber comprise a    glass fiber, a cellulosic fiber, a carbon fiber, a graphite fiber, a    metal fiber, a ceramic fiber, a metallic-ceramic fiber, an aramid    fiber, or any combination thereof.-   22. The centralizer of embodiment 15, wherein the fiber is coated    with a surface coating agent.-   23. A method comprising:    -   providing a centralizer disposed about a wellbore tubular,        wherein the centralizer comprises:        -   a first collar;        -   a second collar;        -   a plurality of bow springs coupling the first collar to the            second collar; and        -   a plurality of particulates disposed on an outer surface of            at least one bow spring;        -   wherein one or more of the first collar, the second collar,            and the bow springs comprise a composite material; and    -   placing the wellbore tubular in a wellbore disposed in a        subterranean formation.-   24. The method of embodiment 23, wherein at least one bow spring has    a multi-step design comprising a plurality of arced sections.-   25. The method of embodiment 23, wherein the particulates comprise    substantially spherical particles.-   26. The method of embodiment 23, wherein the particulates comprise    zirconium oxide.-   27. The method of embodiment 23, wherein the particulates are coated    with a surface coating agent.-   28. The method of embodiment 23, wherein the centralizer is    maintained in position on the wellbore tubular using stop collars,    protrusions, upsets, or any combination thereof.-   29. The method of embodiment 23, wherein the centralizer can rotate    about the wellbore tubular.-   30. The method of embodiment 23, wherein the composite material    comprises a fiber and a matrix material.-   31. The method of embodiment 30, wherein the matrix material    comprises a resin comprising at least one component selected from    the group consisting of: an orthophthalic polyester, an isophthalic    polyester, a phthalic/maelic type polyester, a vinyl ester, a    thermosetting epoxy, a phenolic, a cyanate, a bismaleimide, a nadic    end-capped polyimide, a polysulfone, a polyamide, a polycarbonate, a    polyphenylene oxide, a polysulfide, a polyether ether ketone, a    polyether sulfone, a polyamide-imide, a polyetherimide, a polyimide,    a polyarylate, a liquid crystalline polyester, a polyurethane, a    polyurea, and any combinations thereof.-   32. The method of embodiment 30, wherein the matrix material    comprises a resin comprising a hardenable resin and a hardening    agent.-   33. The method of embodiment 32, wherein the hardenable resin    comprises at least one component selected from the group consisting    of: a bisphenol A diglycidyl ether resin, a butoxymethyl butyl    glycidyl ether resin, a bisphenol A-epichlorohydrin resin, a    bisphenol F resin, a polyepoxide resin, a novolak resin, a polyester    resin, a phenol-aldehyde resin, a urea-aldehyde resin, a furan    resin, a urethane resin, a glycidyl ether resin, and any    combinations thereof.-   34. The method of embodiment 32, wherein the hardening agent    comprises at least one component selected from the group consisting    of: a cyclo-aliphatic amine, an aromatic amine, an aliphatic amine,    an imidazole, a pyrazole, a pyrazine, a pyrimidine, a pyridazine, a    1H-indazole, a purine, a phthalazine, a naphthyridine, a    quinoxaline, a quinazoline, a phenazine, an imidazolidine, a    cinnoline, an imidazoline, a 1,3,5-triazine, a thiazole, a    pteridine, an indazole, an amine, a polyamine, an amide, a    polyamide, a 2-ethyl-4-methyl imidazole, and any combinations    thereof.-   35. The method of embodiment 30, wherein the fiber is coated with a    surface coating agent, and wherein the surface coating agent    comprises at least one compound selected from the group consisting    of: a silazane, a siloxane, an alkoxysilane, an aminosilane, a    silane, a silanol, a polyvinyl alcohol, and any combination thereof.-   36. A method comprising:    -   providing a centralizer disposed about a wellbore tubular,        wherein the wellbore tubular comprises a stop collar, a        protrusion, or an upset on either end of the centralizer, and        wherein the centralizer comprises:        -   three or more collars;        -   a plurality of bow springs comprising a plurality of            portions of bow springs, wherein each portion of bow springs            couples two adjacent collars, and wherein one or more of the            collars and the bow springs comprise a composite material;            and    -   placing the wellbore tubular in a wellbore disposed in a        subterranean formation.-   37. The method of embodiment 36, wherein the bow springs in at least    two adjacent portions are longitudinally aligned in an offset    pattern.-   38. The method of embodiment 36, further comprising a plurality of    particulates disposed along an outer surface of at least one bow    spring.-   39. The method of embodiment 36, wherein the composite material    comprises a fiber and a matrix material.-   40. The method of embodiment 39, wherein the matrix material    comprises a resin comprising a hardenable resin and a hardening    agent.-   41. The method of embodiment 39, wherein the fiber is coated with a    surface coating agent, and wherein the surface coating agent    comprises at least one compound selected from the group consisting    of: a silazane, a siloxane, an alkoxysilane, an aminosilane, a    silane, a silanol, a polyvinyl alcohol, and any combination thereof.-   42. The method of embodiment 23, wherein at least one bow spring has    a plurality of particulates disposed on an outer surface and has a    multi-step design comprising a plurality of arced sections.-   43. A centralizer produced from a process comprising:    -   forming a plurality of composite bow spring from a fiber and a        resin;    -   disposing a plurality of particulates on an outer surface of the        composite bow springs;    -   curing the composite bow springs in a desired shape to form a        plurality of cured bow springs;    -   disposing a first portion of a resin-wetted fiber about a        cylindrical mandrel to form a plurality of collars;    -   disposing the plurality of cured bow springs onto the mandrel        with the bow spring ends in contact with the first portion of        resin-wetted fiber;    -   disposing a second portion of the resin-wetted fiber about the        cylindrical mandrel; curing the collars to form a cured        centralizer; and    -   pressing the mandrel out of the cured centralizer.-   44. The centralizer of embodiment 43, wherein the fiber is supplied    as a filament, a yarn, a tow, a roving, a tape, a fabric, or any    combination thereof.-   45. The centralizer of embodiment 43, wherein the fiber in the    composite bow spring is aligned in a longitudinal direction.-   46. The centralizer of embodiment 43, wherein the fiber in the    collars is aligned in a circumferential direction.-   47. The centralizer of embodiment 43, wherein the process comprises    an automated process.-   48. The centralizer of embodiment 47, wherein the automated process    considers a diameter of the fiber, a stiffness of the fiber, a    moduli of the fiber, a cost of the fiber, or any combination    thereof.

What is claimed is:
 1. A centralizer comprising: a first collar; asecond collar; a plurality of bow springs coupling the first collar tothe second collar; and a plurality of particulates disposed on an outersurface of at least one bow spring, wherein at least a portion of theplurality of particulates are partially embedded within the outersurface of the at least one bow spring, and wherein the plurality ofparticulates is configured to reduce the running forces during movementof the centralizer when the plurality of particulates are in contactwith a surface; wherein one or more of the first collar, the secondcollar, and the bow springs comprise a composite material.
 2. Thecentralizer of claim 1, wherein the leading or trailing edges of thefirst collar or the second collar are tapered or angled.
 3. Thecentralizer of claim 1, wherein the centralizer further comprises athird collar, wherein the plurality of bow springs comprise a firstportion of bow springs and a second portion of bow springs, and whereinthe first portion of the bow springs couple the first collar to thethird collar and the second portion of the bow springs couple the secondcollar to the third collar.
 4. The centralizer of claim 1, wherein atleast one bow spring has a multi-step design comprising a plurality ofarced sections.
 5. The centralizer of claim 1, wherein the thickness ofat least one bow spring varies along the length of the bow spring. 6.The centralizer of claim 1, wherein the particulates comprisesubstantially spherical particles.
 7. The centralizer of claim 1,wherein the particulates have a size ranging from about 0.001 inches toabout 0.2 inches.
 8. The centralizer of claim 1, wherein theparticulates comprise a metal or ceramic.
 9. The centralizer of claim 1,wherein the particulates comprise zirconium oxide.
 10. The centralizerof claim 1, wherein the particulates are coated with a surface coatingagent.
 11. The centralizer of claim 1, wherein the composite materialcomprises a fiber and a matrix material.
 12. The centralizer of claim11, wherein the fiber comprise a glass fiber, a cellulosic fiber, acarbon fiber, a graphite fiber, a metal fiber, a ceramic fiber, ametallic-ceramic fiber, an aramid fiber, or any combination thereof. 13.The centralizer of claim 11, wherein the fiber is coated with a surfacecoating agent.
 14. The centralizer of claim 1, wherein the particulateshave a lower coefficient of friction with the surface than the outersurface of the at least one bow spring with the surface.
 15. Thecentralizer of claim 1, wherein that at least one bow spring comprisesthe composite material, and wherein at least the portion of theplurality of particulates are partially embedded and cured within thecomposite material on the outer surface of the at least one bow spring.16. A centralizer comprising: three or more collars; a plurality of bowsprings comprising a plurality of portions of bow springs, wherein eachportion of bow springs couples two adjacent collars, and wherein one ormore of the collars and the bow springs comprise a composite material;and wherein at least one bow spring comprises a plurality of arcedsections, wherein a thickness of a first arced section of the pluralityof arced sections is less than a thickness of a second arced section ofthe plurality of arced sections; and a plurality of particulatesdisposed along the outer surface of at least one bow spring.
 17. Thecentralizer of claim 16, wherein the bow springs in adjacent portionsare longitudinally aligned in an offset pattern.
 18. The centralizer ofclaim 16, wherein the number of bow springs in a first portion and asecond portion are different.
 19. The centralizer of claim 16, whereinthe composite material comprises a fiber and a matrix material.
 20. Thecentralizer of claim 19, wherein the fiber comprise a glass fiber, acellulosic fiber, a carbon fiber, a graphite fiber, a metal fiber, aceramic fiber, a metallic-ceramic fiber, an aramid fiber, or anycombination thereof.